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Imbalance between IQ outputs on ADL5380

Question asked by ytc on Nov 8, 2016
Latest reply on Nov 15, 2016 by hkumar

I'm using the ADL5380 evaluation board to demodulate an RF signal at its base frequency into IQ channels. I changed the eval board from AC-coupled single-ended configuration to DC-coupled differential outputs for the IQ channels according to the datasheet. Then I recorded the IQ outputs as I changed the phase of the LO signal between 0-360 degrees. I did see oscillations as a function of the phase in both channels. However, the amplitudes of the oscillation were very different. The Q amplitude was about 5x of that in the I channel. I checked the board and the downstream amplifiers and didn't see anything obviously wrong. Then I suspected that the chip might be damaged internally. So I replaced the chip with a brand new one. It was still the same. I wonder if anyone has any clue about what might go wrong. Thanks!